The structure and composition of normal and psoriatic horny cells will be studied. Normal horny cells will be scraped from different body regions and scales obtained from involved and uninvolved skin of patients. The filament protein (keratin) will be extracted with 8 M urea and 25 mM 2-mercaptoethanol in Tri-HC1 buffer 8 and reconstituted filaments prepared by dialysis against low ionic strength buffer. The matrix proteins will be extracted with alkaline buffer containing reducing agent. Specimens of reconstituted filaments, matrix proteins and mixtures of reconstituted filaments and matrix proteins will be investigated in the electron microscope. The polypeptide chains of filament and matrix proteins will be characterized by slab gel electrophoresis.